As is known, ultraviolet (UV) radiation emitted at certain wavelengths is mutagenic to microorganisms. Subtype C of the UV spectrum (UVC), also referred to as “germicidal” UV radiation, is generally considered to be radiation emitted at wavelengths in the range of 100-280 nanometers. In one application, UV radiation emitted at approximately 253.7 nanometers may be used to “inactivate” (i.e., destroy, render harmless, and/or prohibit the growth or reproduction of) certain microorganisms.
It is common to refer to a “dosage” of UVC radiation, a product of the UVC radiation intensity and exposure time, required to inactivate a particular microorganism. A dosage is typically measured in units of microwatt seconds per square centimeter (μW·s/cm2). Different dosages are required to inactivate different microorganisms. For example, a dosage of 12,100 μW·s/cm2 may be needed for a 3-log (99.9%) inactivation of methicillin resistant Staphylococcus aureus (MRSA), a dosage of 11,500 μW·s/cm2 may be needed for a 3-log inactivation of clostridium difficile, and a dosage of 8,400 μW·s/cm2 may be needed for a 3-log inactivation of vancomycin-resistant enterococci.
Prevention of infection by certain microorganisms is often an important concern in places where microorganisms may be widespread, including hospitals, laboratory settings, gyms, locker rooms, among many others. In a hospital operating room, for example, it may be important to inactivate microorganisms at the surgical site and on the many surfaces in the operating room, such as the operating table. This is often accomplished with the use of specialized UV lamp fixtures surface-mounted on the ceiling of the operating room. A variable transformer (Variac) is used to adjust the intensity of these lamps depending on whether surgery is occurring or whether it is desired to “bathe” the operating room in UV radiation. Alternatively or in addition, this may be accomplished via a mobile UV lamp system 10 disposed on a rolling base 12 and comprising a plurality of UV lamps 14, as shown in FIG. 2. One example of lamp system 10 may be the ARTZ Mobile Room Germicidal UVC Solution offered by American Air & Water, Inc. of Hilton Head Island, S.C.
Further, it may be important to inactivate microorganisms in the upper air, as convection currents can carry such microorganisms throughout the room. In this regard, FIG. 1 is a table describing various potentially airborne nosocomial pathogens. Targeting microorganisms in the air may be done using the mobile lamp system 10, described above, or using specialized UV lamp fixtures directly mounted on the walls of the operating room, typically at a height of approximately 8 feet. These lamp fixtures often operate at full intensity, even during surgical procedures. An example of a prior art, wall-mounted UVGI fixture 16 configured to inactivate microorganisms in the air is shown in FIG. 3. UVGI fixture 16, which as shown may be similar to the TB-W UVGI fixture offered by American Air & Water, Inc., may comprise adjustable louvers 18 to allow a user to direct the UV radiation in a desired direction.